Rubber composition

ABSTRACT

The tackiness of a terpolymer rubber of ethylene, propylene and a nonconjugated diene is remarkably improved by incorporating therein (1) an alkylphenol-formaldehyde resin, alkylphenolacetaldehyde resin, or alkylphenol-acetylene resin and (2) a thermoplastic resin produced by the polymerization of olefinic unsaturated hydrocarbons derived from the cracking of petroleum hydrocarbons, and containing substantially no aromatic hydrocarbons. This effect of the specific combination of two kinds of resin is synergetic. In addition to the improved tackiness, said rubber composition retains an excellent age resistance and a high capacity for loading fillers, both characteristics being inherent in said terpolymer rubber.

United States Patent 1 Oguri et al.

[ 1 Jan. 2, 1973 [s41 RUBBER COMPOSITION [75] Inventors: Hiroki Oguri,Toyonaka; Hideo Nagasaki, Minoo, both of Japan [22] Filed: Feb. 18, 1970[21] Appl. No.: 12,455

[30] Foreign Application Priority Data March a, 1969 Japan ..44/17768 52US. Cl. .....260/848, 260/23.7 M, 260/33.6 AQ,

- 260/38, 260/415 R, 260/897 R, 260/897 A 51 rm. Cl. ..C08g37/16, C08d9/08, 008d 9/10 58 Field 61 Search ..260/845, 848, 897 R, 897 A,

3,070,570 12/1962 Gessler et a1. ..260/897 R 3,299,170 1/1967 Gonzenbach..260/848 3,334,063 8/1967 Berliner ..260/897 R 3,354,107 11/1967 Hamed..260/848 3,402,140 9/1968 Bickel et a1... ..260/848 3,514,417 5/1970Bickel et al ..'....260/848 Primary Examiner-John C. BleutgeAttorney-Stevens, Davis, Miller & Mosher [5 7] ABSTRACT The tackiness ofa terpolymer rubber of ethylene,

propylene and a nonconjugated diene is remarkably improved byincorporating therein (1) an alkylphenolformaldehyde resin,alkylphenol-acetaldehyde resin, or alkylphenol-acetylene resin and (2) athermoplastic resin produced by the polymerization of olefinicunsaturated hydrocarbons derived from the cracking of petroleumhydrocarbons, and containing substantially no aromatic hydrocarbons.This effect of the specific combination of two kinds of resin issynergetic. In addition to the improved tackiness, said rubbercomposition retains an excellent age resistance and a high capacity forloading fillers, both characteristics being inherent in said terpolymerrubber.

8 Claims, No Drawings l RUB BER COMPO SITION This invention relates toan ethylene-propylene-nonconjugated diene terpolyrner rubber(hereinafter referred to as EPDM) composition with improved tackiness.

Whereas EPDM has an excellent age resistance, a

- high capacity for loading fillers, and other valuable properties, ithas, on the other hand, serious disadvantages including a poortackiness, an insufficient mechanical fatigue resistance, and a low tearcharacteristics. To overcome these disadvantages, there have beenproposed various tackifiers for EPDM, such as for examplealkylphenol-formaldehyde resins, alkylphenolacetylene resins,xylene-formaldehyde resins, coumarone-indene resins, etc. However, nosatisfactory result has,-heretofore, been obtained.

than that expectable from the respective effects of. the components Aand B when used alone. For instance,

the results as shown in Table l were obtained in the case of anethylene-propyiene-ethylidene norborneiie I terpolymer rubber.

TABLE 1 Composition No. i n III' IV (Zomponent A Ethylene-propylene- Thepresent inventors had investigated on the increased tackifying effect ofmixtures of two kinds of tackifier, and, as a result, disclosed that thetackiness of synthetic rubbers suchas SBR, IlR, CR and NBR could beremarkably increased due to the synergetic effect, by incorporatingtherein a reactive alkylphenol-formaldehyde resin together with apetroleum resin produced by the polymerization ofa petroleum fractioncontaining hydrocarbons having four or more carbon atoms (see JapanesePat. Publication No. 17,659/66). Said combination of two types of resin,however, was found not so effectivein improving the tackiness of EPDM asmight become of a commercial importance. As a result offurtherinvestigations, we have now found that .when a special grade ofthe so-called petroleum resin, which consists essentially of aliphatichydrocarbons accompanying practicallyno aromatic hydrocarbons, is usedin combination with an alkylphenol-formaldehyde resin,alkylphenol-acetaldehyde resin, or an alkylphenol-acetylene resin, thetackiness of EPDM can be increased by the synergetic effect to the levelthat is desirable for commercialization, said high level being entirelyunexpectable from the performance of a mixture of analkylphenol-formald'ehyde resin and the usual petroleum resin containing'anappreciable amount of aromatic hydrocarbons (Cf. Table l).

' An object of the present invention is to provide an EPDM compositionhaving an increased tackiness.

Another object of the'invention is to provide an EPDM composition whichretains the excellent properties inherent inEPDM and having, inaddition, suffi-.

cient tackiness to be put into industrialpractice. Other objectsandmeritsof the invention will become apparent from the followingdescription.

According tothe-present invention, an EPDM composition with improvedtackiness is provided, which comprises (1) EPDM, (2) anvalltylphenol-formaldehyde resin, an alkylphenol-acetaldehyderesin, man

ethylidene norbomene terpolymer rubber (parts by weight) Reactiveoctylphenolfomialdehyde resin (parts by weight) 5 Petroleum resincontaining aromatic hydrocarbons (Petrosin, trade mark of MitsuiPetrochemical) (parts by weight) Petroleum resin containing no aromatichydrocarbons (fPiccopale", trade mark of Esso Chemicals) (parts byweight) Tackines (g/cm) As is clear from Table l, the combination ofcomponents A and B exhibits a synergetic effect. The discovery of thisfact by the present inventors, which was surprisingly unexpected, hasled to the present invention which is of a high commercial value in thatit facilitates the industrial application of EPDM.

The EPDM composition of the invention retains the advantageousproperties of EPDM such as an excellent age resistance and a desirablehigh capacity for loading fillers, and no significant change isrecognized in other alkylphenol-acetylene resin (hereinafter referredto-as properties.

The use of the component A or B alone as a tackifier for rubber is knownin prior art. However, the synergetic efi'ect upon EPDM of the specificcombination of these two components according to thepresent invention isnot predictable from prior knowledge.

The alkylphenols in the alkylphenol-formaldehyde resin,alkylphenol-acetaldehyde resin and alkylphenolacetylene resin which areused as the component A in the present invention, are phenolssubstituted by alkyl groups having one to 12 carbon atoms, such as forexample m-cresol, m-isopropylphenol, p-tert.-butylphenol, p-tert.-octylphenol, p-nonylphenol, p-ndodecylphenol, etc., or mixtures of thesephenols. More particularly, the following alkyl'phenol resins arepreferable as the-component A of the present composition: A reactive ornonreactive p-tert.-octylphenol-formaldehyde resin formed by thecondensation reaction between p-tert.-octylphenol and formaldehyde, andhaving a methylol content of 0 to 15 percent, a softening point of to 110 C., and an acid value of 5 to 50; a p-tert.-butylphenol-acetaldehyderesin formed by the condensation reaction between p-tert.-butylphenoland acetaldehyde, and having a softening point of to 110 C. and aspecific gravity of 1.0 to 1.1; and a ptert.- butylphenol-acetyleneresin produced by the condensation reaction between p-tert.-butylpheno1and acetylene, and having a specific gravity of 1.0 to 1.1 and asoftening point of 100 to 180 C.

The component B of the present composition is a thermoplastic resincontaining substantially no aromatic hydrocarbons, which is produced bythe polymerization of a mixture of monoand di-olefinic unsaturatedhydrocarbons derived from the cracking of petroleum hydrocarbons. Aparticularly preferable resin is produced by polymerizing a mixture ofmonoand di-olefins having five or six carbon atoms and 5- or 6-memberedcyclic mono-and di-olefins, the resultant resin having a softening pointof 70 to 110 C., a molecular weight of 500 to 2,000, and a bromine valueof 20 to 70. This resin is an aliphatic hydrocarbon resin having asaturated or unsaturated 5- or 6-membered ring as a basic structure, andan alkyl group of one to four carbon atoms as a side chain, and containssubstantially no aromatic hydrocarbons. Higher content of the cyclicstructure in the resin results in more striking effect upon theimprovement in tackiness of the present composition containing saidresin. The resin consisting of only aliphatic hydrocarbons is, ofcourse, the most preferable as the component B, but the presence of asmall amount of aromatic hydrocarbons in the resin does not appreciablyaffect the improvement in tackiness and other physical properties of thepresent composition containing said resin.

In the present composition, a weight ratio of component A to component Bcan be varied over a range of l 9 to 9 1, preferably from 2 8 to 5 5.For example, ratios of 2.5 7.5 and 4 6 are both preferable, the maximumsynergetic effect being achieved in the former ratio.

The compounding ratio of EPDM to the sum of components A and B in thepresent composition is 20 parts or less, preferably 5 to parts by weightper 100 parts by weight of EPDM.

The present composition can be prepared by mixing EPDM and thecomponents A and B together in a way similar to that generally used inrubber compounding, such as, for example, by the use'of example, testingroll mill or a Banbury mixer. Alternatively, the present composition canbe produced by compounding into EPDM, by the same means as thatmentioned above, a mixture of the components A and B, which have beenpreviously prepared by mixing both components in molten state. It ,isalso possible that the components A and B are dissolved in and mixedwith, for example, a solution of EPDM in n-hexane obtained in the courseof manufacturing EPDM, and then the n-hexane is removed for recovery togive as a residue the present composition of EPDM.

The present composition may contain other suitable ingredientspreferably used with EPDM, such as fillers, pigments, plasticizers,processing aids, and vulcanizing agents including particularly sulfur orother compounds acting similarly to sulfur, and vulcanizationaccelerators.

The EPDM employed in the present composition is a terpolymer ofethylene, propylene and a nonconjugated diene such as dicyclopentadiene,1,4-hexadiene, methylene norbomene, ethylidene norbomene, 1,5-cyclooctadiene, all of these dienes being well known in the art.

The tackiness of the present composition was evaluated by measuring thetackiness of test pieces by the well-known pick-up method (using anautomatic pickup tackmeter made by Toyo Seiki Seisaku-Sho Ltd.),

said test pieces being prepared as follows: EPDM, the

components A and B, and the usual compounding ingredients for rubberwere milled in a usual way to produce an EPDM compound, which was thenformed into a sheet on a calender roll, and thereafter the 'surface ofthe sheet was conditioned for one day before making the measurement.

In the case of a rubber composition containing a conventional tackifier,the tackiness of the calendered sheet prepared therefrom generally tendsto decrease when the surface of the sheet is aged for a long period oftime. Contrary to this general tendency, the tackiness of the presentcomposition rather increases with the ageing of the surface, thephenomenon being one of the features of the present composition.

The rubber compositions of the present invention can be used in anyapplication of the EPDM.

The features of this invention will be further illustrated in detailwith reference to the following examples. These examples are notintended to limit the invention. In the examples, all parts andpercentages are by weight.

EXAMPLE 1 Parts Stearic acid 1 zinc oxide 5 HAF black Process oil 40Tetramethylthiuram monosultide l .5 Mercaptobenzothiazole 0.5 sulfur 1.5

The EPDM rubber used was a terpolymer rubber of ethylene, propylene anddicyclopentadiene (Royalene 301, trade mark of Uniroyla Co.). Thealkylphenolformaldehyde resin used was a nonreactivetert.-octylphenol-formaldehyde resin having a methylol content of2-percent or less, a softening point of 935 C., and an acid value of21.3. The thermoplastic petroleum resin used was Piccopale (trade mark;a product of Esso Chemicals Co.) having a softening point of 100 C., amolecular weight of 1400, and a bromine value of 36, and consisting ofan aliphatic hydrocarbon containing no aromatic hydrocarbons and havinga 6-membered ring as a basic structure and a methyl group as a sidechain. The tackiness of the compositions were as shown in Table 2. As isclearly seen from the Table, the tackiness of each composition from (B)to (E) of the present invention which contains both components A and Bwas far superior to that'of the compositions (A) and (F) containingeither the compount A alone or the component B alone.

prepared in the following manner:

An alkylphenol-formaldehyde resin and a thermoplastic resin were mixedin molten state in a proportion of 25 75 and the resultant mixture wasdissolved in a solution of a terpolymer rubber of ethylene, propyleneand ethylidene norbomene in n-hexane, and

then the n-hexane was removed for recovery to give as the residue theEPDM compositions, the proportions of said resin mixture to the rubbercomponent therein being as shown in Table 3. Thealkylphenol-formaldehyde resin used was a reactivep-tert.-octylphenolformaldehyde resin having a methylol content of 10percent, a softening point of 91 C., and an acid value of 22.3. Thethermoplastic resin used was prepared by polymerizing a mixture ofmonoolefi'nic and diolefinic unsaturated. hydrocarbons having five tosix carbon atoms, the content of -membered ring component intheresultant aliphatic resin being 12 percent.

Ea'ch composition (l-l), (I), (J) and (K) was compounded on a testingroll mill with the following ingredients for rubber compounding:

Parts Stearic acid 1 Zinc oxide 5 l-lAF black 50 Process oil ITetramethylthiuram monosulfide l .5 Mercaptobenzothiazole 0.5 Sulfur I1.5

The tackiness of each compound was measured to obtain the results asshown in Table 3. As is clearly seen from Table 3, the tackiness of eachof the compositions (H), (l), (J) and (K) prepared in accordance withthe present invention was far superior to that of a control composition(G). The tackiness of a composition containing 5 parts'(per 100 parts ofEPDM) of the abovementioned p-tert.-octylphenol-formaldehyde resinalone, and that of a composition containing 5 parts of theabove-mentioned thermoplastic resin consisting of w an aliphatichydrocarbon containing 12 percent of a 5- membered ring component was280 and 310 g/cm,

respectively.

TABLE3 CompositionNo. (o (H) (l) (.1) (K) 15thylene-propyleneethylidenenorbomene terpolymerrubber 100 100 100 100 100 (parts) Mixture ofresins,

mixed in molten state Tackiness (g/cm) A tackiness larger than 1,000g'lcm shows that the tackiness Wu unable to be measured owing to themeasuring capacity of the testing machine used.

EXAMPLE 3 The changes with the lapse of time in the surface tackiness ofthe composition (H) in Example 2 were measured to obtain the results asshown in Table 4. The tackiness of the present composition was found toincrease with the lapse of time.

TABLE 4 Elapsed time (days) 1 3 8 Tackiness (g/cm) 850 970 1 ,000

EXAMPLE 4 One hundred Parts of a terpolymer rubber of ethylene,propylene and 1,4-hexadiene and 10 parts'of a mixture (25 of a reactivep-tert.-butylpheno1- formaldehyde resin containing 10 percent ofmethylol group and a thermoplastic aliphatic resin containing 9 percentof a 5-membered ring component, said mixture being prepared by mixingboth resins in molten state, were compounded in a Banbury mixer with thefollowing ingredients to obtain a composition (L):

Parts Stearic acid l Zinc oxide 5 HAF black 50 Process oil 10Tetrarnethylthiuram monosulfide 1.5 Mercaptobenzothiazole 0.5 Sulfur 1.5

Another composition (M) was prepared in the same manner except for theomission of the addition of the above-mentioned resin mixture. Thecompositions (M) and (N) thus obtained were cured at 160 C. for 1 0minutes. The tackiness of both compositions and the physical propertiesof the cured compositions were measured to obtain the results as showninTable 5.

TABLE 5 Composition No. (L) (M) Ethylene-propylenel ,4-hexadieneterpolymer rubber (parts) 100 Mixture of resins,

mixed in molten state (parts) 10 Tackiness (g/cm) 900 Tensile strength(kg/cm) 224 197 Elongation (5) 750 480 Tensile stres at 300 (kg/cm) 85104 Hardness (Hs) 61 64 Growth rate of flex cracking (times) 7.9 failure(40,000 cycles) (3,000 cycles) Tear strength (kg/cm) 71 58 t remarkablyimproved in the tackiness of uncured compound as well as in' the growthrate of flex cracking and tear strength of the cured compound.

EXAMPLE One hundred Parts of a terpolymer rubber of ethylene, propyleneand dicyclopentadiene, 2.5 parts of a p-tert.-butylphenol-acetyleneresin having a specific gravity of 1.03 and a softening point of 125 to130 C., 7.5 parts of Piccopale 100 (the same as that used in Example 1),and the same amount of the same compounding'ingredients for rubber asthose used in Example 1 were mixed on a testing roll mill to obtain acomposition in accordance with the invention. The tackiness of thiscomposition was 950 g/cm. Further two compositions were prepared in amanner similar to that described above except that 10 parts of eitherthe p-tert.-butylphenol-formaldehyde resin or Piccopale 100 was usedalone instead of using in combination. The tackiness values of thesecompositions were 300 g/cm and 350 g/cm, respectively.

EXAMPLE 6 One hundred Parts of a terpolymer rubber of ethylene,propylene and ethylidene norbomene, 2.5 parts of ap-tert.-butylphenol-acetaldehyde resin having a specific-gravity of 1.05and a softening point of 90 to 95 C., 7.5 parts ofPiccopale 100" (thesame as that in Example 1), and the same amount of the same compoundingingredients for rubber as those used in Example 1 were mixed on atesting roll mill to obtain a composition in accordance with theinvention. The tackiness of the calendered sheet of the composition thusobtained was more than 1,000 g/cm,as measured by a pick-up tackmeter.The tackiness values of two compositions prepared in a manner similarto, that described above except that 10 parts of either theptert.-butylphenol-acetaldehyde resin or Piccopale 100 was used aloneinstead of using in combination were 400 g/cm and 300 g/cm,respectively.

What is claimed is: l. A rubber composition with improved tackiness,consisting essentially of l. a terpolymer rubber of ethylene, propylene,and a non-conjugated diene;

an alkylphenol-formaldehyde resin, alkylphenolacetaldehyde resin, and analkyiphe'ndI-ace tylene resin; and

3. a thermoplastic resin produced by the polymerization of a mixture ofmonoand di-olefins having five or six carbon atoms and having asoftening point of to 110 C, a molecular weight of 500 to 2000 and abromine value of 20 to 70, wherein the ratio by weight of component (2)to component (3) is from 1:9 to 9:1, and the total amount of components(2) and (3) is 20 parts by weight or less per parts by weight ofcomponent l 2. A rubber composition according to claim 1,

wherein the nonconjugated diene component of said terpolymer rubber lSdicyclopentadiene, 1,4-hexadiene, methylene norbomene, ethylidenenorbomene, or l,5cyclooctadiene.

3. A rubber composition according to claim 1, wherein the component (2)is a resin produced by reacting a phenol substituted by an alkyl grouphaving one to 12 carbon atoms with formaldehyde, acetaldehyde, oracetylene.

4. A rubber composition according to claim 3, wherein the alkylphenol ism-cresol, misopropylphenol, p-tert.-butylphenol, p-tert.-octylphenol,p-nonylphenol, or p-n-dodecyclphenol, or mixture thereof. I V

5. A rubber composition according to claim 1, which contains, inaddition, ingredients generally used for rubber compounding.

6. A rubber. composition according to claim 1, wherein the total amountof the components (2) and (3) is 5 to 15 parts by weight per 100 partsby weight of the component (1 7. A rubber composition according to claim1, wherein the component (2) is an alkylphenol-formaldehyde resin or analkylphenol-acetylene resin.

8. A rubber composition according to claim 1, wherein the component (2)is an alkylphenol-acetaldehyde resin. I

a component selected from the group consisting of

2. a component selected from the group consisting of analkylphenol-formaldehyde resin, alkylphenol-acetaldehyde resin, and analkylphenol-acetylene resin; and
 2. A rubber composition according toclaim 1, wherein the nonconjugated diene component of said terpolymerrubber is dicyclopentadiene, 1,4-hexadiene, methylene norbornene,ethylidene norbornene, or 1,5-cyclooctadiene.
 3. a thermoplastic resinproduced by the polymerization of a mixture of mono- and di-olefinshaving five or six carbon atoms and having a softening point of 70* to110* C, a molecular weight of 500 to 2000 and a bromine value of 20 to70, wherein the ratio by weight of component (2) to component (3) isfrom 1:9 to 9:1, and the total amount of components (2) and (3) is 20parts by weight or less per 100 parts by weight of component (1).
 3. Arubber composition according to claim 1, wherein the component (2) is aresin produced by reacting a phenol substituted by an alkyl group havingone to 12 carbon atoms with formaldehyde, acetaldehyde, or acetylene. 4.A rubber composition according to claim 3, wherein the alkylphenol ism-cresol, m-isopropylphenol, p-tert.-butylphenol, p-tert.-octylphenol,p-nonylphenol, or p-n-dodecyclphenol, or a mixture thereof.
 5. A rubbercomposition according to claim 1, which contains, in addition,ingredients generally used for rubber compounding.
 6. A rubbercomposition according to claim 1, wherein the total amount of thecomponents (2) and (3) is 5 to 15 parts by weight per 100 parts byweight of the component (1).
 7. A rubber composition according to claim1, wherein the component (2) is an alkylphenol-formaldehyde resin or analkylphenol-acetylene resin.
 8. A rubber composition according to claim1, wherein the component (2) is an alkylphenol-acetaldehyde resin.